System and method for cleaning and recovery of hydrocarbons

ABSTRACT

A system has a heater that heats a contaminated input hydrocarbon to a process temperature. An ionizer applies an electron inducing voltage to the heated hydrocarbon and a flocculent supply provides a charged flocculent into the ionized hydrocarbon. A separator removes the flocculent and contaminants from the hydrocarbon to produce solid waste and oil.

CROSS-REFERENCE TO RELATED CASES

This application claims the benefit of U.S. provisional patent application Ser. No. 61/787,477, filed on Mar. 15, 2013, and incorporates such provisional application by reference into this disclosure as if fully set out at this point.

FIELD OF THE INVENTION

This disclosure relates to oil production in general and, more particularly, to cleaning of soil and recovery of hydrocarbons therefrom.

BACKGROUND OF THE INVENTION

For many years, waste materials such as hazardous and non-hazardous waste oil sludges from petroleum production, transportation, and refineries were impounded in basins with little thought to their final disposition. These waste sludges come from American Petroleum Institute (API) and Dissolved Air Flotation (DAF) separator bottoms, tank bottoms, spills, heat exchanger sludge, secondary emulsions, slop oil, and other sources. Some of these waste materials have been classified by the Environmental Protection Agency as hazardous waste, which therefore restricts their removal from the generation site for treatment and/or disposal. It is presently acceptable to land farm the wastes using specially developed strains of bacteria for decomposition of the oil. However, the heavy metal contents of the oil left behind in the soil presents potential groundwater and controlled run-off contamination to the environment. Furthermore, the oil contained in the sludge is not recovered for reuse or recycling.

Other related waste products that remain an unutilized source or environmental contamination are acid tars. Acid tars are the remains of an antiquated refining process that leaves extremely heavy, viscous material that has a very low pH level. Acid tars have historically been generated as by-products of benzole refining, refining petroleum fractions (particularly white oil) and oil re-refining. The nature of the acid tars will depend to a degree on their origin. For example, acid tar arising from a specialist refinery processes involving the treatment of petroleum fractions with sulphuric acid may comprise black, tarry deposits. However, that from washing of benzole (BTX fractions) with sulphuric acid may be an odorous dark colored liquid. Acid tars have a highly variable composition between sites and even within one lagoon, but are usually characterized by a weathered, crusty and relatively solid surface, with more fluid tars below. In situ, acid tar comprises a mass of hydrocarbons that is generally viscous and tarry with low pH. Layers of acid tar may be separated with intermittent soil layers or other deposited wastes. Surrounding soils are likely to be contaminated to varying degrees with tars and hydrocarbons as well.

Some lagoons, in particular the older ones, are likely to have been filled with untreated tars. This was done either as a temporary measure to allow weathering to reduce the acidity, prior to disposal or incineration, or as the permanent disposal method. More recently deposited lagoons may contain partially treated tars. Treatment may have been by the use of lime, in an attempt at neutralization, or by igniting the tars in situ. In some cases, attempts will usually have been made at covering or capping the tars, often with soil, sand, ash or domestic refuse. However, fluid tars can ‘bleed’ to the surface and solid capping material may sink into them. The tars that rise to the surface can expand and soften further in the sun and, potentially, may overflow resulting in movement off-site. Some acid tar lagoons have also been used as disposal sites for other materials and it is not uncommon to find other wastes such as demolition materials and chemical drums in the lagoons. Acid tars are extremely difficult to handle and process because of their thickness and acidity level.

What is needed is a system and method for addressing the above and related problems.

SUMMARY OF THE INVENTION

The invention of the present disclosure, in one aspect thereof comprises a system having a heater that heats a contaminated input sludge to a process temperature. The system includes an ionizer applies an electron inducing voltage to the heated sludge and a flocculent supply provides a charged flocculent into the ionized sludge. The system also includes a separator that removes the flocculent and contaminants from the sludge to produce solid waste and oil.

In some embodiment, the separator removes water from the oil and may comprise a three phase horizontal decanter centrifuge. The flocculent may comprise a polyelectrolyte copolymer. Some embodiments include a heated conveyor that moves the solid waste and applies heat thereto, and a condenser for reclaiming hydrocarbon evaporates from the solid waste. The aforementioned heater may comprise a vertical heat exchanger.

The system may include a transfer pump and a hydrocarbon source heater. The hydrocarbon source heater heats contaminated input sludge at a hydrocarbon source to a pumping temperature for pumping toward the ionizer by the pump. The system may include a melting tank that receives the input sludge from the transfer pump and/or a feed pump that moves the input sludge from the melting tank and into the heater, and ionizer.

The invention of the present disclosure, in another aspect thereof, comprises a system having a grinder that grinds tars and a heater that heats the tar to a liquefied state. The system includes a sodium hydroxide supply that provides a sodium hydroxide solution to the liquefied tar and a diluent supply that provides a diluent to the liquefied tar. In the present system an ionizer applies an electron inducing voltage to the liquefied tar and a flocculent supply provides a flocculent to the ionized tar. The system includes a decanter that separates solids from the tar.

In some embodiments, the decanter comprises a two stage horizontal centrifuge decanter. The system may also include a three phase horizontal centrifuge decanter that further separates additional sediment from the tar and produces oil and water from the remaining tar. The flocculent may comprise a polyelectrolyte copolymer and the diluent comprises one of diesel or a gas oil.

The invention of the present disclosure, in another aspect thereof, comprises a method including heating a contaminated hydrocarbon, applying a voltage to the hydrocarbon to ionize the contaminants, and infusing the ionized hydrocarbon with a flocculent to coalesce contaminants. The coalesced contaminants are removed to produce solid waste and oil from the contaminated hydrocarbon.

In some embodiments, removing the coalesced contaminant comprises decanting the hydrocarbon in a three phase horizontal centrifuge decanter producing solid waste, oil, and water. The method may also include decanting the hydrocarbon in a two phase centrifuge decanter to remove a first quantity of solids from the hydrocarbon, and then decanting the hydrocarbon in a three phase horizontal centrifuge decanter producing solid waste, oil, and water. In some embodiments, the contaminated hydrocarbon is ground before being further processed by heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process level diagram of one embodiment of a hydrocarbon recovery system according to the present disclosure is shown

FIG. 2 is a schematic diagram of the system of FIG. 1.

FIG. 3 is a process level diagram of another embodiment of a hydrocarbon recovery system according to the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a process level diagram of one embodiment of a hydrocarbon recovery system according to the present disclosure is shown. The system 100 is simplified to the basic process according to the present embodiment for purposes of illustration. One of ordinary skill in the art will appreciate that, like many processes, various details may be implemented in different ways. More detailed examples are provided below.

In the present embodiment, a hydrocarbon source 102 is accessed. The hydrocarbon source may be a waste sludge or another substance containing hydrocarbons and various other materials and contaminants that are not suited for use with the hydrocarbons or as a feedstock. Contaminants may include, but are not limited to, soil, sand, clay, drilling mud, water, acidic or basic chemicals, non-desirable organics, and heavy metals.

The sludge 102 is heated at step 104. Depending upon the constituency of the sludge 104, an ideal process temperature for the sludge is from about between 75° and 100° C. A preferred process temperature is where the specific gravity of the oil, water, and solids has the highest differential. Also preferred is temperature is where the viscosity of the oil within the sludge 104 has reached its lowest level below the boiling point of the sludge. Other process temperatures may also be suitable so long as the sludge is heated sufficiently to allow contaminants, water, and oil in the sludge to flow separately.

The heated sludge is exposed to an ionization apparatus at step 106. The ionizer applies an electron inducing high voltage to the heated sludge. The voltage may range from about 12 to about 24 VDC and has an effect of ionizing non-ionized particles and droplets or increasing the charge on low-charged materials. The electrons moved into the sludge and onto the non-charged or low-charge particles and droplets will place a negative charge on the same.

The ionized sludge is mixed in mixer 108 with a flocculent polyelectrolyte copolymer 110. The polymer 110 is flocculates the solid particles and contaminants in the sludge that were ionized previously into larger masses. The polymer 110 also works to combine water droplets and oil droplets in the sludge into larger masses, thereby enhancing separation ability.

The previously heated, ionized, and flocculated sludge is now fed into a separator 112. In various embodiments, the separator 112 may be a three-phase horizontal decanter centrifuge. This device separates the solid contaminants and those coalesced by the polymer 110 as a solid waste product 120 expelled at a first outlet 114. The solid waste 120 may be disposed of accordingly based upon its makeup. The remaining liquid is further separated based upon its relative density. Water 122, being heavy compared to oil 124 is expelled at a second outlet 116. At this point, the water 122 should be clean enough to be treated for reuse with normal commercial water purification systems. A third outlet 118 provides the purified oil 124. As used in this disclosure, the term oil is taken to mean any reclaimed hydrocarbon with a suitable makeup for refining, distilling, or otherwise used in industry. Contaminants and water having been removed from the sludge 102, oil 124 that was otherwise lost, wasted, or destined for land farming may be reclaimed for industrial use.

Referring now to FIG. 2, a more detailed schematic diagram of the system 100 is shown. The system 100 may utilize different types of heat sources including steam boilers or one or more thermal fluid heaters. A steam boiler is a heater that converts heat energy into water as a medium. The water is converted to steam in which the temperature is controlled by the pressure in the boiler, with the higher pressure allowing higher steam temperatures.

The present embodiment utilizes a thermal fluid heater 208. This type of heater utilizes spiral coils inside a vessel where thermal fluid is circulated in a closed loop system. The thermal fluid is heated by combusting a fuel (e.g., natural gas, fuel oil, etc.) In a burner where the flame passes through the heating coil. Some embodiments may utilize a thermal fluid heater with capacities on the order of millions of British Thermal Units (BTU's). The thermal fluid heater 208 of the present embodiment has a capacity of 6 million BTU's.

A circulation pump 206 pumps the thermal fluid to various locations in the system 100 as needed. A thermal fluid supply line 204 may be routed to, or tapped by, various process locations as needed. One such location, in the present embodiment, is a heat exchanger 206 placed in the oil sludge 102. Coils in the heat exchanger 206 expose the oil sludge 102 to heat from the thermal fluid. In some embodiments, the oil sludge 102 is maintained at a near steady temperature while being fed into the rest of the process. A thermal fluid return line 210 may be used by the heat exchanger 202 and other devices for return thermal fluid flow back to the fluid heater 208.

A transfer pump moves the heated sludge from its heated source to be processed. In some embodiments, the transfer pump is capable of handling sludge that comprises up to 99% of either oil or water, and up to 50% solid matter. A melting tank 212 may be utilized for either further heating or maintaining the heat of the sludge using another heat exchanger 213. The melting tank 212 may also have an agitator for keeping the sludge from settling before further processing.

A feed pump 214 moves the sludge from the melting tank 212 (if present) toward or into the ionizer 106. However, in some embodiments, the sludge is heat again (or further) by a heat exchanger 216. A spiral heat exchanger may be used here. Spiral heat exchangers have a cylindrical shape with flat, wide coils inside the cylindrical vessel. The flow of the sludge travels in a spiral pattern through the exchanger coils in an inside to outside flow. Heating medium from the fluid heater 208 may pass through the coils inside the exchanger 216 while the sludge flows outside the coils. Thus, as with previous heat exchangers discussed herein, the heating medium is completely isolated from the sludge. Due in part to the shape and orientation of the exchanger 216, solid matter in the sludge is flushed though the exchanger, with little risk of accumulation. The heat exchanger 216 heats the oil sludge to the optimal process temperature (e.g., between 75° and 100° C.). The optimal process temperature is where the specific gravity of the oil, water, and solids has the highest differential.

Where an ionizer 106 is utilized, it may be configured as a preferably cylindrical apparatus with at least one rod anode, which is surrounded with a coaxial cylindrical dielectric sheath, at least one rod cathode which is surrounded with a coaxial cylindrical dielectric sheath, and at least one cylindrical mesh grid, which is coaxial with and surrounds the cathode. Both ends of the cylindrical chamber are hermetically capped by a mounting fixture made to provide a waterproof fit. The ionizer may use a converter that converts various commercial alternating voltages, including 120, 230, 380 and 460, to a direct current of between 12 and 24, which are supplied to the cathode. The effect of the ionizer is to apply a high electron-inducing voltage to the sludge so that non-ionized or low charge ionic materials are ionized, thereby placing a negative charge on the particles and droplets in the sludge.

A cationic (positively charged) copolymer 110 may be applied from a polymer supply to the ionized sludge to flocculate and coagulate the solid particles and liquid droplets in the sludge. The larger mass of solids will separate much more effectively in the centrifuge 112 than the smaller, un-flocculated material. The polymer will also combine the water droplets and oil droplets into larger masses, thereby enhancing separation.

Suitable polyelectrolyte copolymers are available from BASF and SNF. The polymer may be an organic chemical compound that consists of an acrylamide that is loaded with positive, neutral, or negative charges. These charged molecules attach to the oppositely charged particles in the oil sludge, much like a magnet. The molecule will attach to thousands of tiny particles to form one large particle. In one preferred embodiment, the preferred polymer comprises quaternized polyacrylamide copolymers in an emulsion form. These products are available in dry, emulsion and solution forms. They are copolymers of acrylamide with a cationic monomer. For various embodiments of the present disclosure, emulsions are considered to be liquids comprised of oil droplets dispersed in water or water droplets dispersed in oil. Emulsion polymers benefit from the fact that they are very easy to put into solution and are quite concentrated (25% to 50%, typically) even though they usually have very high molecular weights. Also, their low bulk viscosity and liquid form makes them very easy to handle, especially in automated systems. They can be diluted by a variety of methods ranging from simply pouring them into the vortex of mixing water to sophisticated dilution systems which require very little manpower to operate. Dilution levels of these products are limited by viscosity so the upper limit is usually 2% to 3%. In practice, however, it is usually better to dilute to 0.5% to 1.0%. This permits the full dissolution of the polymer. If lower dilutions are to be used, they may be diluted from this stock solution.

The polymer 110 may be blended with water in a high-shear environment. This process is called “making down” the polymer. Polymer droplets are emulsified in a mineral oil for storage and require a “breaking up” of the droplets to expose the polymer to water, which activates the charged molecules. The polymer 110 is usually mixed in a 0.25 to 1% solution in the water. The diluted polymer is then usually dosed into the sludge at a rate of 100 to 1,000 parts per million. The dosing may occur as the ionized sludge enters the separator or centrifuge 112, or may occur as a separate previous step via a separate mixing apparatus (not shown).

Once the sludge has been surfactant treated or dosed with the polymer 110, it may be separated in the centrifuge 112. In one embodiment, the centrifuge 112 is a three phase, horizontal decanter style machine. This type of machine has a solid bowl, with a conical and cylindrical sections. Inside the bowl, there is a helical conveyor (or “scroll”) with flights that follow the bowl shape. The scroll turn independently of the bowl, which enables the separated solid matter to settle and convey up the conical section and exit the machine. The sludge enters the centrifuge through the feed pipe and is then accelerated to rotation speed in the core of the centrifuge. The accelerated material then enters the bowl of the centrifuge where is separates under high G forces. The solid matter will settle to the outer most part of the bowl, then the water will form the next layer, and the oil will settle at the highest level. The solids are conveyed to the solid discharge end of the machine by the scroll.

The oil and water follow a helical path to the liquid end of the machine, where they are separated. There are different types of separation devices that are utilized in three phase decanters. In one type, the water flows over a weir where it is ejected into the collection vessel. The oil is removed by an adjustable skimming device that allows the fluid level to be adjusted while the machine is in operation. The water level is adjusted to where only water flows over the phase weir, and only the oil flows out of the skimming device. This type of machine is from Hydro Pure Technologies, Inc. under model names STS 200, STS 300, or STS 550.

Another type of oil/water separation device is one manufactured by Flottweg GHMB. This type of separation device utilizes a skimmer mounted on an eccentric base that is controlled by rotating the feed tube. The skimmer is raised and lowered to adjust the fluid level in the machine. Inside the machine, nozzles are mounted to allow the oil phase to exit the machine under gravity pressure. The fluid that is not ejected from the nozzles is ejected through the skimmer under pressure. The skimmer is adjusted to allow the purified oil to flow out the nozzles and the separated water to be ejected out the skimmer.

It should be understood that the systems and method of the present disclosure may utilize any number of suitable centrifuges or separation apparatus. Three outputs are provided from the centrifuge 112. The now purified hydrocarbons or oil 124 is provided at outlet 118. A holding tank 119 may be provided until the oil 125 can be removed for use (e.g., by a truck or pipeline). Water 122 is provided at the outlet 116 and may be reused or further purified by known commercial water treatment systems. The water provided from the centrifuge 112 will have less than 500 PPM oil remaining therein.

Sediment or solid wastes from the centrifuge may be expelled at the outlet 114. A conveyor system 218 may be provided for moving the sediment away. In some embodiments, the sediment is conveyed to a thermal conveyor 222 which applies heat to the sediment. The heat causes any residual hydrocarbons to evaporate or cook out of the sediment. The fumes may be trapped in a condenser 224 to produce condensed hydrocarbons 226. The condensed hydrocarbons 226 may be added to the oil 124 from the centrifuge 112. The sediment or solid waste 120 will have less than 1000 PPM oil remaining after the final heating step.

As a method, in various embodiments the above system may be summarized as a process for the recovery of oil, useful for further processing as refinery feed stock or as fuel oil, from waste oil sludge containing oil, water, and solids. The systems and methods of the present disclosure are useful to recover the oil from sludges that cannot be separated by normal mechanical means heretofore known or practiced. The method includes (a) heating sludge 102 to a temperature sufficient to liquefy and lower the specific gravity of oil in the sludge to below 0.95; (b) treating the heated sludge with high electron-inducing voltage in the ionizer 106; (c) injecting a cationic polyacrylamide copolymer 110 to flocculate the solid particles and coalesce the oil and water droplets; (d) centrifuging the resulting oil sludge from step (b and c) to separate oil 124, water 122 and solids 120; (e) recovering oil 124 from said centrifuging for further refinery processing and/or fuel oil, and; (f) recovering water 122 from said centrifuging, whereby said water is sufficiently clean for further treatment in a conventional water treatment.

Referring now to FIG. 3, a process level diagram of another embodiment of a hydrocarbon recovery system 300 according to the present disclosure is shown. The system 300 shares some common components with the system 100 shown in FIGS. 1-2. The additions and modifications of the system 200, relative to the system 100, enable the present system 200 to be highly suited for use in treatment of acid tars.

The tar 301 is excavated from lagoons 302 using an excavator (not shown) and feeding the solid tar 301 into a large grinder 304. In some embodiments the capacity of the grinder 304 is 50 tons or more of asphalt per hour. The ground tar is heated at a temperature sufficient to liquefy and lower the specific gravity of the oil in the tar to below 0.95. If needed, the tar may be diluted with a cutter-stock 308 such as diesel or gas oil, to further reduce the viscosity and specific gravity of the tar. The acid tar may be neutralized with a sodium hydroxide solution 310 from a sodium hydroxide supply and blended therein in a high shear-blending vessel 306. An amount of sodium hydroxide required to raise the pH of the tar to a range between 5 and 7 may be utilized. The needed heat may be applied while the tar is in the shearing vessel 306 or may be a separate step or vessel that may include a heat exchanger as previously described or otherwise known in the art.

The pH adjusted tar may be treated with high electron-inducing voltage in the ionizer 106 condensing the oil and water in the tar. If needed, cationic polyacrylamide copolymer 110 may be injected to flocculate the solid particles and coalesce the oil and water droplets. If needed, a separate blending vessel or mixer 108 may be used to disperse the copolymer 110 into the tar. The resulting mixture may be centrifuged in a two phase horizontal decanter centrifuge 312 to separate oil and water from the solid material (or “ash”) 314. The tar may be centrifuged again in the three phase centrifuge 112 decanter to separate the liquid tar (now oil 124) from the water 122 and remaining solid matter or sediment 122. The oil 124, water 122, and sediment 122 will have the same purity properties as previous described with respect to the system 100.

It will also be understood that the system diagram 300 is simplified in order to highlight the modification that make it particularly suited to the treatment of acid tars. It is understood that various heaters, conveyors, stirrers, condensers, and other implements may be utilized where needed based upon reference to the system diagram 200 or as otherwise known to one of skill in the art.

Thus, the present invention is well adapted to carry out the objectives and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those of ordinary skill in the art. Such changes and modifications are encompassed within the invention as defined by the claims. 

What is claimed is:
 1. A system comprising: a heater that heats a contaminated input sludge to a process temperature; an ionizer that applies an electron inducing voltage to the heated sludge; a flocculent supply that provides a charged flocculent into the ionized sludge; and a separator that removes the flocculent and contaminants from the sludge to produce solid waste and oil.
 2. The system of claim 1, wherein the separator removes water from the oil.
 3. The system of claim 2, wherein the separator comprises a three phase horizontal decanter centrifuge.
 4. The system of claim 1, wherein the flocculent comprises a polyelectrolyte copolymer.
 5. The system of claim 1, further comprising a heated conveyor that moves the solid waste and applies heat thereto and a condenser for reclaiming hydrocarbon evaporates from the solid waste.
 6. The system of claim 1, wherein the heater comprises a vertical heat exchanger.
 7. The system of claim 1, further comprising a transfer pump and a hydrocarbon source heater, wherein the hydrocarbon source heater heats contaminated input sludge at a hydrocarbon source to a pumping temperature for pumping toward the ionizer by the pump.
 8. The system of claim 7, further comprising a melting tank that receives the input sludge from the transfer pump.
 9. The system of claim 8, further comprising a feed pump that moves the input sludge from the melting tank and into the heater, and ionizer.
 10. A system comprising: a grinder that grinds tars; a heater that heats the tar to a liquefied state; a sodium hydroxide supply that provides a sodium hydroxide solution to the liquefied tar; a diluent supply that provides a diluent to the liquefied tar; an ionizer that applies an electron inducing voltage to the liquefied tar; a flocculent supply that provides a flocculent to the ionized tar; and a decanter that separates solids from the tar.
 11. The system of claim 10, wherein the decanter comprises a two stage horizontal centrifuge decanter.
 12. The system of claim 11, further comprising a three phase horizontal centrifuge decanter that further separates additional sediment from the tar and produces oil and water from the remaining tar.
 13. The system of claim 10, wherein the flocculent comprises a polyelectrolyte copolymer.
 14. The system of claim 10, wherein the diluent comprises one of diesel or a gas oil.
 15. A method comprising: heating a contaminated hydrocarbon; applying a voltage to the hydrocarbon to ionize the contaminants; infusing the ionized hydrocarbon with a flocculent to coalesce contaminants; and removing the coalesced contaminants to produce solid waste and oil from the contaminated hydrocarbon.
 16. The method of claim 15, wherein removing the coalesced contaminant comprises decanting the hydrocarbon in a three phase horizontal centrifuge decanter producing solid waste, oil, and water.
 17. The method of claim 15, wherein removing the coalesced contaminants comprises: decanting the hydrocarbon in a two phase centrifuge decanter to remove a first quantity of solids from the hydrocarbon; and decanting the hydrocarbon in a three phase horizontal centrifuge decanter producing solid waste, oil, and water.
 18. The method of claim 15, further comprising grinding the contaminated hydrocarbon. 